Question

The Cambrian explosion refers to (a) a dramatic increase in animal diversity beginning about 542 million years ago; (b) the Impact that killed the dinosaurs; (c) the sudden emergence of eukaryotic life in the geological record dating to about 2.1 billion years ago.

Short answer

The Cambrian explosion refers to (a) a dramatic increase in animal diversity beginning about 542 million years ago.

Step-by-step solution

Understanding the Context

The Cambrian explosion refers to a specific period in Earth's history. It was a time of significant change in the diversity of life forms on Earth.

Relating Options to Historical Events

(a) The Cambrian explosion involved a dramatic increase in animal diversity, which aligns with a known historical period that started around 542 million years ago. (b) The impact that killed the dinosaurs happened around 66 million years ago and is unrelated to the Cambrian period. (c) The emergence of eukaryotic life around 2.1 billion years ago happened much earlier than the Cambrian explosion.

Choosing the Correct Answer

Among the given options, the Cambrian explosion is most accurately described by option (a): a dramatic increase in animal diversity beginning about 542 million years ago.

Key concepts

Animal Diversity

The concept of animal diversity refers to the wide variety of animal forms that exist on Earth. The Cambrian Explosion is a key event related to this diversity. It marks a time when there was a significant increase in the number and variety of animal species.
This sudden burst of life forms took place about 542 million years ago and is notable for the appearance of many of the major animal phyla we recognize today.
At this time, organisms developed distinct body plans, which included:

• Shells
• Skeletons
• Different appendages

This period marked the first time that complex animals became predominant, showcasing a level of structural diversity that was unprecedented. It laid the foundation for the diverse ecosystems we see in the modern world.

Earth's History

Earth's history is a fascinating tale that covers billions of years. It's a timeline filled with dramatic changes and significant events, one of which is the Cambrian Explosion. This pivotal event took place during the Paleozoic Era, a time when Earth experienced dramatic biological and geological transformations.
Before the Cambrian Period, Earth was home mostly to tiny, simple life forms. During and after this period, life on Earth experienced tremendous growth in complexity and variety.
Several factors played into the conditions that may have facilitated this explosion of life:

• Environmental changes such as increased oxygen levels in the seas
• Evolutionary innovations leading to more complex organisms
• Ecological interactions that spurred rapid diversification

These aspects of history help us understand how different factors combined to create a planet teeming with the life forms we see today.

Geological Periods

Geological periods are divisions of time that help us understand Earth's history in a structured way. The Cambrian Explosion took place during the Cambrian Period, part of the Paleozoic Era.
This period is known for its revolutionary biological changes. It signifies a key chapter in Earth's geological timeline where countless animal species appeared in the fossil record for the first time.
The Cambrian Period, starting approximately 542 million years ago, followed the mysterious Ediacaran Period. During this earlier time, soft-bodied multicellular organisms were prevalent. Some interesting features of the Cambrian include:

• The emergence of hard-bodied creatures preserved in fossils
• The development of different ecological niches among animals
• The establishment of predator-prey relationships in ecosystems

Understanding geological periods gives us insights into how life has evolved over millions of years amidst changing environmental conditions.

Eukaryotic Life

Eukaryotic life consists of organisms whose cells contain a nucleus enclosed within membranes. These are distinct from simpler life forms, such as bacteria, which are considered prokaryotic.
The discovery of eukaryotic life dates back to about 2.1 billion years ago, which precedes the Cambrian Explosion by a significant margin. However, this earlier emergence set the stage for the development of complex multicellular organisms that would later diversify in the Cambrian Explosion.
The evolutionary step from prokaryotic to eukaryotic life involved:

• Complex cell structures, including organelles like mitochondria and chloroplasts
• Increased biological capabilities that allowed the formation of multicellular beings
• The ability to sustain more complex forms of life, which paved the way for animal diversity

Eukaryotic life is central to the story of life's complexity on Earth, bridging microbial beginnings with the explosion of varied animal forms seen during the Cambrian.